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<i class='fas fa-caret-right ms-1'></i></div><div id=sidebar-toc class="hidden md:block overflow-y-auto mx-6 md:mx-0 pe-6 pt-2 md:max-h-doc-sidebar bg-primary-bg md:bg-transparent"><div class="flex flex-wrap ms-4 -me-2 p-2 bg-secondary-bg md:bg-primary-bg rounded"><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/>汇编语言</a></div><ul class=ps-6><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/18/>11.9 ~ 11.11</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/17/>11.7 ~ 11.9</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/16/>11.1 ~ 11.6</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/15/>10.8 ~ 10.12</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/14/>10.1 ~ 10.7</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/13/>9.7 ~ 9.9</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/12/>9.1 ~ 9.6</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/11/>8.5 ~ 8.9</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/10/>8.1</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/9/>7.1 ~ 7.10</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/8/>6.1 ~ 6.3</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/7/>5.1 ~ 5.4</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/6/>4.1 ~ 4.9</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/5/>3.6 ~ 3.10</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/4/>3.1 ~ 3.5</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/3/>2.8 ~ 2.12</a></div></li><li class=py-2><div><a class="text-eureka hover:text-eureka" href=https://b.hui.ke/docs/assembly-language/2/>1.11 ~ 2.6</a></div></li><li class=py-2><div><a class=hover:text-eureka href=https://b.hui.ke/docs/assembly-language/1/>1.1 ~ 1.10</a></div></li></ul></div></div></div><div class="w-full md:w-3/4 lg:w-4/5 pb-8 pt-2 md:pt-8"><div class=flex><div class="w-full lg:w-3/4 px-6"><article class=prose><h1 class=mb-4>1.11 ~ 2.6</h1><div class="text-tertiary-text not-prose mt-2 flex flex-row flex-wrap items-center"><div class="me-6 my-2"><i class="fas fa-calendar me-1"></i>
<span>2020-03-03</span></div><div class="me-6 my-2"><i class="fa-solid fa-pen-to-square me-1"></i>
<span>2020-03-03</span></div><div class="me-6 my-2"><i class="fas fa-clock me-1"></i>
<span>4 min read</span></div><div class="me-6 my-2"><i class="fas fa-folder me-1"></i>
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<a href=https://b.hui.ke/series/x86asm-language/ class=hover:text-eureka>x86asm Language</a></div><div class="me-6 my-2"><i class="fa-solid fa-eye me-1"></i>
<span id=busuanzi_value_page_pv><i class="fa fa-spinner fa-spin"></i></span> Hits</div></div><p>  《汇编语言（第3版）》1.11 ~ 2.6、《零基础入门学习汇编语言》P5 ~ 8</p><h3 id=111-内存地址空间概述>1.11 内存地址空间（概述）</h3><p>  一个 CPU 的地址线宽度为 10，那么可以寻址 1024 个内存单元，这 1024 个可寻到的内存单元就构成这个 CPU 的内存地址空间。</p><h3 id=113-接口卡>1.13 接口卡</h3><p>  CPU 对外部设备不能直接控制，如显示器、音箱、打印机等。直接控制这些设备进行工作的是插在扩展插槽上的接口卡。</p><h3 id=114-各类存储器芯片>1.14 各类存储器芯片</h3><ol><li>从读写属性上分两类<ol><li>随机存储器（RAM）</li><li>只读存储器（ROM）</li></ol></li><li>从功能和连接上分类<ol><li>随机存储器 RAM</li><li>装有 BIOS 的 ROM</li><li>接口卡上的 RAM</li></ol></li></ol><h3 id=115-内存地址空间>1.15 内存地址空间</h3><p>  最终运行程序的是 CPU，我们用汇编编程的时候，<strong>必须要从 CPU 角度考虑问题</strong>（学习汇编的核心思维）。</p><h2 id=第二章-寄存器cpu工作原理>第二章 寄存器（CPU工作原理）</h2><p>  一个典型的 CPU 由<strong>运算器、控制器、寄存器</strong>等器件组成，这些器件靠内部总线相连。</p><p>  8086 CPU 有 14 个寄存器，它们的名称为：AX、BX、CX、DX、SI、DI、SP、BP、IP、CS、SS、DS、ES、PWS。</p><h3 id=21-通用寄存器>2.1 通用寄存器</h3><p>  8086 CPU 所有的寄存器都是 16 位的，可以存放两个字节。</p><p>  AX、BX、CX、DX 通常用来存放一般性数据被称为通用寄存器。</p><p>  一个 16 位寄存器所能存储的数据的最大值为 $ 2^{16}-1 $</p><p>  8086 上一代 CPU 中的寄存器都是 8 位的，所以为保证兼容性，这四个寄存器都可以分为两个独立的 8 位寄存器使用：AX 可以分为 AH 和 AL；BX 可以分为 BH 和 BL，以此类推。</p><h3 id=22-字在寄存器中的存储>2.2 字在寄存器中的存储</h3><p>  一个字可以存在一个 16 位寄存器中，这个字的高位字节和低位字节自然就存在这个寄存器的高 8 位寄存器和低 8 位寄存器中。</p><h3 id=23-几条汇编指令>2.3 几条汇编指令</h3><blockquote><p>汇编指令不区分大小写</p></blockquote><table><thead><tr><th style=text-align:left>汇编指令</th><th style=text-align:left>控制 CPU 完成的操作</th><th style=text-align:left>用高级语言的语法描述</th></tr></thead><tbody><tr><td style=text-align:left>mov ax,18</td><td style=text-align:left>将 18 送入 AX</td><td style=text-align:left>AH = 18</td></tr><tr><td style=text-align:left>mov ah,78</td><td style=text-align:left>将 78 送入 AH</td><td style=text-align:left>AH = 78</td></tr><tr><td style=text-align:left>add ax,8</td><td style=text-align:left>将寄存器 AX 中的数值加上 8</td><td style=text-align:left>AX = AX + 8</td></tr><tr><td style=text-align:left>mov ax,bx</td><td style=text-align:left>将寄存器 BX 中的数据送入寄存器 AX</td><td style=text-align:left>AX = BX</td></tr><tr><td style=text-align:left>add ax,bx</td><td style=text-align:left>将 AX，BX 中的内容相加，结果存在 AX 中</td><td style=text-align:left>AX = AX + BX</td></tr></tbody></table><p>  CPU 执行下表中的程序段的每条指令后，对寄存器中的数据进行的改变。</p><p>问1：原 AX 中的值：0000H，原 BX 中的值：0000H）</p><table><thead><tr><th style=text-align:left>程序段中的指令</th><th style=text-align:left>指令执行后 AX 中的数据</th><th style=text-align:left>指令执行后 BX 中的数据</th></tr></thead><tbody><tr><td style=text-align:left>mov ax,4E20H</td><td style=text-align:left>4E20H</td><td style=text-align:left>0000H</td></tr><tr><td style=text-align:left>add ax,1406H</td><td style=text-align:left>6226H</td><td style=text-align:left>0000H</td></tr><tr><td style=text-align:left>mov bx,2000H</td><td style=text-align:left>6226H</td><td style=text-align:left>2000H</td></tr><tr><td style=text-align:left>add ax,bx</td><td style=text-align:left>8226H</td><td style=text-align:left>2000H</td></tr><tr><td style=text-align:left>mov bx,ax</td><td style=text-align:left>8226H</td><td style=text-align:left>8226H</td></tr><tr><td style=text-align:left>add ax,bx</td><td style=text-align:left>?</td><td style=text-align:left>8226H</td></tr></tbody></table><p>  答案：044CH（原本 8226H+8226H=<strong>1</strong>044CH，但是 ax 只放得下两个字所以是 044CH）</p><p>问2：原 AX 中的值：0040H</p><table><thead><tr><th style=text-align:left>程序段中的指令</th><th style=text-align:left>指令执行后 AX 中的数据</th></tr></thead><tbody><tr><td style=text-align:left>add al,85H</td><td style=text-align:left>00C5H</td></tr><tr><td style=text-align:left>add al,93H</td><td style=text-align:left>?</td></tr></tbody></table><p>  答案：0058H（因为 add 的地方是 al 八位寄存器，所以原本属于 ax 高位 ah 的 01 进位值会被丢失。这里的丢失，指的是进位值不能在 8 位寄存器中保存，但是 CPU 并不是真的丢弃这个进位值）</p><h3 id=24-物理地址>2.4 物理地址</h3><p>  CPU 访问内存单元时要给出内存单元的地址。所有的内存单元构成的存储空间是一个一维的线性空间，这个唯一的地址称为物理地址。</p><h3 id=25-16-位结构的-cpu>2.5 16 位结构的 CPU</h3><p>  概括的讲，16 位结构描述了一个 CPU 具有以下几个方面特征</p><ol><li>运算器一次最多可以处理 16 位的数据。</li><li>寄存器的最大宽度为 16 位。</li><li>寄存器和运算器之间的通路是 16 位的。</li></ol><h3 id=26-8086-cpu-给出物理地址的方法>2.6 8086 CPU 给出物理地址的方法</h3><p>  8086 有 20 位地址总线，可传送 20 位地址，寻址能力为 1M（ $ 2^{20}=1MB $ ）</p><p>  8086 内部为 16 位结构，它只能传送 16 位的地址，表现出的寻址能力就只有64K（ $ 2^{16}=64KB $ ）</p><p>  8086 CPU 采用一种在内部用两个 16 位地址合成的方法来形成一个 20 位的物理地址</p><p>  地址加法器合成物理地址的方法：物理地址 = 段地址 × 16 + 偏移地址</p><p>  “段地址 × 16”有一个更为常用的说法就是数据左移 4 位（二进制位）。</p><table><thead><tr><th style=text-align:left>移位位数</th><th style=text-align:left>二进制</th><th style=text-align:left>十六进制</th><th style=text-align:left>十进制</th></tr></thead><tbody><tr><td style=text-align:left>0</td><td style=text-align:left>10B</td><td style=text-align:left>2H</td><td style=text-align:left>2</td></tr><tr><td style=text-align:left>1</td><td style=text-align:left>100B</td><td style=text-align:left>4H</td><td style=text-align:left>4</td></tr><tr><td style=text-align:left>2</td><td style=text-align:left>1000B</td><td style=text-align:left>8H</td><td style=text-align:left>8</td></tr><tr><td style=text-align:left>3</td><td style=text-align:left>10000B</td><td style=text-align:left>10H</td><td style=text-align:left>16</td></tr><tr><td style=text-align:left>4</td><td style=text-align:left>100000B</td><td style=text-align:left>20H</td><td style=text-align:left>32</td></tr></tbody></table><ol><li>通过观察上表（移位次数和各种形式数据的关系）得出<ol><li>一个数据的二进制形式左移 1 位，相当于该数据乘以 2；</li><li>一个数据的二进制形式左移 N 位，相当于该数据乘以 $ 2^N $</li><li>地址加法器完成段地址 × 16 的运算即以二进制形式存放的段地址左移 4 位。</li></ol></li><li>进一步思考可得<ol><li>一个数据的十六进制形式左移 1 位，相当于乘以 16；</li><li>一个数据的十进制形式左移 1 位，相当于乘以 10；</li><li>一个数据的 X 进制形式左移 1 位，相当于乘以 X。</li></ol></li></ol></article><div class=my-4><a href=https://b.hui.ke/tags/%E5%AF%84%E5%AD%98%E5%99%A8/ class="inline-block bg-tertiary-bg text-sm rounded px-3 py-1 my-1 me-2 hover:text-eureka">#寄存器</a>
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hidden px-6 pb-6 lg:block"><nav id=TableOfContents><ul><li><ul><li><a href=#111-内存地址空间概述>1.11 内存地址空间（概述）</a></li><li><a href=#113-接口卡>1.13 接口卡</a></li><li><a href=#114-各类存储器芯片>1.14 各类存储器芯片</a></li><li><a href=#115-内存地址空间>1.15 内存地址空间</a></li></ul></li><li><a href=#第二章-寄存器cpu工作原理>第二章 寄存器（CPU工作原理）</a><ul><li><a href=#21-通用寄存器>2.1 通用寄存器</a></li><li><a href=#22-字在寄存器中的存储>2.2 字在寄存器中的存储</a></li><li><a href=#23-几条汇编指令>2.3 几条汇编指令</a></li><li><a href=#24-物理地址>2.4 物理地址</a></li><li><a href=#25-16-位结构的-cpu>2.5 16 位结构的 CPU</a></li><li><a href=#26-8086-cpu-给出物理地址的方法>2.6 8086 CPU 给出物理地址的方法</a></li></ul></li></ul></nav></div><script>window.addEventListener("DOMContentLoaded",()=>{enableStickyToc()})</script></div></div></div></div></div><script>document.addEventListener("DOMContentLoaded",()=>{hljs.highlightAll(),changeSidebarHeight(),switchDocToc()})</script></div></div></main><footer class=pl-scrollbar><div class="mx-auto w-full max-w-screen-xl"><div class="text-center p-6 pin-b"><script async src=/js/click.js></script><div id=poem_ip></div><script type=text/javascript>jinrishici.load(function(e){tags.innerHTML=e.data.matchTags})</script><div><span id=timeDate>载入年天数...</span><span id=times>载入时分秒...</span>
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